Centennial, Colorado (CNN) — Police are eager to learn why Karl Pierson opened fire with a shotgun at his Colorado school Friday.

They have asked his parents and will search their home Saturday, but the person who could best answer the question lay lifeless Friday night on the floor of Arapahoe High School in the Denver suburb of Centennial.

The body of the 18-year-old student remained there as part of the crime scene he created when he wounded a student then shot himself, the sheriff said.